save stderr to file in case it is useful

diff --git a/tests/TESTonce b/tests/TESTonce
index 79336b4d9c741b9f6a483775cc6bd9e5bf7bbc0c..a52b7f7b75a160115bd00206cae41fefea60a12d 100755 (executable)
--- a/tests/TESTonce
+++ b/tests/TESTonce
@@ -30,7 +30,7 @@ if ($^O eq 'MSWin32') {
 else {
     # we used to do this as a nice pipeline, but the problem is that $r fails to
     # to be set properly if the tcpdump core dumps.
-    $r = system "$TCPDUMP 2>/dev/null -# -n -r $input $options >NEW/$outputbase";
+    $r = system "$TCPDUMP 2>NEW/$outputbase.stderr -# -n -r $input $options >NEW/$outputbase";
     if($r != 0) {
         my $coredump = false;
         my $status = 0;